It is believed Astori died of "cardio-circulatory arrest due to natural causes" - a type of heart attack - but that he showed "no warning signs" of having any illness, said Udine prosecutor Antonio De Nicolo.

Club spokesman Arturo Mastronardi said: "The lad did not turn up to the team breakfast at 9.30am and he was usually the first to arrive.

"So they went to check on him. Davide was sleeping in a room on his own. The body has been taken for an autopsy, which I think will be conducted today."

A club statement read: "A profoundly shocked Fiorentina are compelled to announce that their captain Davide Astori, who was struck by an unexpected sudden illness, has passed away.

Fiorentina captain and Italy international football player Davide Astori's body removed by coroner

DAVIDE ASTORI - WHAT WE KNOW SO FAR:

Astori travelled with Fiorentina squad on Saturday ahead of Serie A clash with Udinese

When club captain did not arrive at team breakfast at 9.30am, team-mates broke down hotel room door to find Astori dead

Astori died of natural causes, aged 31, in his sleep - with no warning signs

"For this terrible and delicate situation, and above all out of respect for his family, we appeal to the sensitivity of the media."

Astori, who was born in the province of Bergamo, passed away ahead of his side's Serie A game against Udinese. All seven of today's fixtures in the Italian top flight have been postponed as a mark of respect.

WATCH: Antonio Conte's touching tribute to Fiorentina captain, Davide Astori, who he managed when with the national team. 😪👏🇮🇹 pic.twitter.com/UhYTqrV0UB

The club is devastated to learn of the death of Davide Astori. The thoughts of everyone at AS Roma are with the player's family, friends and teammates at this terrible and tragic time. pic.twitter.com/vDlL4LIkJr

A man who loved football and who grew up as footballer with us. #ACMilan are shocked by the passing of Davide #Astori. It is with great sadness that we offer our deepest condolences to his family and closed ones and to ACF Fiorentina

His former club Roma tweeted: "The club is devastated to learn of the death of Davide Astori. The thoughts of everyone at AS Roma are with the player's family, friends and team-mates at this terrible and tragic time."

A tweet from Juventus' official account read: "On this day of tragedy, Juventus expresses its deepest condolences to Davide Astori's family and Fiorentina."